It seemed that our nursery rhymes___ some magic because all the nights I sang them for my daughter, she would listen to them with keen pleasure．

A．must have had

B．should have had

C．could have had

D．need have had

在附件安装中，尾纤必须用（）管保护后走线用扎带固定在走线架上。

A、PVC管

B、波纹

C、铁管

D、热缩管